Small clean up of fuse code.

- Add TEMP_FAILURE_RETRY around all relevant system calls.
- Cleanup some of the read calls.
- Add error log messages when read/write calls do not actually read/write the
  expected number of bytes.
- Add error messages for write failures in fuse_status/fuse_replay.

Test: Attached to the sdcard process and stepped through most of the modified
Test: code. Also, create/read/write/delete files in /storage/emulated/0
Test: directory.

Change-Id: I73e4c0db861960f4c0af1bf96b06cd61fa74be69